First things first: yes, you will likely wait a long time to get in to see a doctor at this walk-in clinic, but without an appointment, is that such a big surprise?
Since I don't yet have a family doctor in Toronto, I went to this walk-in clinic the week after Christmas, and while I waited about 2 hours before I was seen by a doctor, Dr. Yang took her time listening to my questions and addressing my concerns once I got in to see her.
If you need immediate attention, go to an emergency room. Otherwise, go to the walk-in clinic, bring a book, and just be patient.